Handcrafted superior quality glass. Hygienic, non-porous borosilicate glass is the healthier choice for brewing tea and ensuring your tea tastes as pure as possible. Steep-range thermometer. The thermometer highlights the optimal steep ranges for white/green, oolong, and black/herbal teas. Two-in-one heat and steep. Heat water then steep tea all with one vessel. The loose tea filter conveniently sits in the kettle. Glass withstands boiling water (212°f).